Spyware will be installed in terms of Cookies Files when you open a site pop up window will get open Like Adds..Some of this type of Add's Will be saved in your PC without your prior notice. Use Some anti spyware tools n also Block pop ups in browser..

SpyWare, MalWare etc can go undetected in many ways. Security vulnerabilities, users carelessly downloading, new forms of malware can also go undetected if security software hasn't been updated to detect ... as well as many other means.

As for javascript operating on the client side, it really depends on browser setting, wary users and vulnerabilities as to how successful an attack can be.

Spyware is a type of malware that can be installed on computers without their knowledge and collects usre personal information. Spyware will be installed in terms of Cookies Files when you open a site pop up window will get open. To remove these spyware from your pc download antispyware software. This is the best solution to get rid of it.